Transistor ignition system having primary circuit resistance control



April 27, 1965 INVENTOR5 BROOKS H. SHORT RICHARD L. SPRAGUE THEIR ATTORNEY United States Patent 1 3 180,997 TRANSISTOR IGNITION SYSTEM HAVING PRI- MARY CIRCUIT RESISTANCE CONTROL Brooks H. Short and Richard L. Sprague, Anderson, Ind.,

assignors to General Motors Corporation, Detroit,

Mich., a corporation of Delaware Filed Sept. 21, 1961, Ser. No. 139,747 Claims. (Cl. 290-38) function of system voltage.

It is well known that in motor vehicle electrical systems the system voltage which is available to supply the DC.

, loads including the ignition system varies widely under diiferent conditions of operation. Thus, during the time that the cranking motor is energized for cranking the engine, the system voltage drops and the extent of this drop varies in accordance with the temperature in which cranking occurs. In very cold weather the drop in voltage is higher than the drop in voltage that will occur during warm temperatures. As cranking is terminated, the sys tern voltage rises and rises still further when the engine is running to drive the generator which then charges the battery and also supplies the DC. loads of the motor vehicle including the ignition system.

In the past, it has sometimes been the practice to place a resistor in a primary circuit of the ignition system and this resistor is shorted out whenever the cranking motor is energized to therefore reduce the resistance of the primary circuit at a time when the system voltage is lowered. Typical systems of this type are shown in the patents to Redick 2,807,729, Leece 1,214,555, and Mallory 1,769,- 150. Although, the above described system of these patents has been successful in conventional ignition systems it is apparent that they do not compensate for any other condition than the condition that the starting motor is being energized. Thus, the systems do not take into account the varying amount of voltage drop that will occur under different temperature conditions and under difterent conditions of charge of the battery. Where a transistor is used to control current flow in the primary circuit of an ignition system, the voltage applied to and the current flow through the transistor must be carefully controlled so that the transistor will not be overloaded and burned out.

It accordingly is an object of this invention to provide an ignition system wherein a transistor controls current flow in the primary circuit of the ignition system and wherein the resistance of the primary circuit is controlled as a function of system voltage.

Another object of this invention is to provide a transistor ignition system wherein a resistor is placed in the primary circuit of the ignition system and. wherein this resistor is short circuited by a relay, the'relay being an accurately calibrated relay which only operates when the system voltage rises above a predetermined value.

1 A further object of this invention is to provide an ignition vsystem wherein a transistor controls current flow in the primary circuit of the ignition system and wherein means are provided for varying ther'esistance of the primary circuit in accordance with system voltage and when the cranking motor is being energized. I i Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein prev ferred embodiments of the present invention are clearly shown.

3,180,997 Patented Apr. 27, 1965 The single figure drawing is a schematic circuit illustration of an ignition system made in accordance with this invention.

Referring now to the drawing, the reference numeral 10 designates a storage battery in a motor vehicle electrical system. One side or" this storage battery 10 is grounded whereas the opposite side of the battery is connected with a power terminal 12. The system voltage of the motor vehicle electrical system will appear between junction 12 and ground and this voltage will vary under different conditions of operation. The battery It) is charged from a generator 14 connected between ground and the power terminal 12. The generator 14 can be a DC. generator or could be an alternator fitted with rectifiers. Where a D0. generator is used, a suitable cutout relay is connected between the junction 12 and one terminal side of the generator 14. The generator 14 is driven by the internal combustion engine 16 of the motor vehicle.

The power terminal 12 is connected with a lead wire 18 and this lead wire is connected with a switch 20 having fixed contacts 22 and 24. This switch includes a movable contactor 26 which is operable to connect contacts 22 and 24 with lead wire 18 in one position of the switch. In another position of the switch, the lead wire 18 is connected only with the contact 22 and in still another position of the switch, the lead wire 18 is disconnected from both contacts 22 and 24. The switch 20 may be a key controlled switch which operates to energize the ignition system from contact 22 and the cranking motor from con- -tor 32 is connected to one side of the starting motor 36 by lead wire 40. In actual practice, the relay coil 30 may be a part of the cranking motor assembly and may also shift a pinion into engagement with the ring gear of the engine 16 in a manner Well known to those skilled in the art. It is seen that when the shifta ble contactor 2s connects lead Wire 18 and junction 28, the relay coil Winding 30 is energized to cause the contactor 32 to shift into engagement with the fixed contact 34, and therefore causes the starting motor 36 to be energized from lead wire 38 The ignition system of this invention includes an accurately calibrated relay 42 which has a relay actuating coil 44- and a shiftable contactor 36 that at times engages the fixed contact 48. The relay 42 is designed such that the contacts 46 and 4-8 are normally in engagement and will only separate when a voltage is impressed across the actuating coil 44 which is greater than a predetermined voltage. This voltage may be by way of example and not by way of limitation 9 volts in a 12 volt system.

The junction 28 is connected to one side of relay actuating coil 44 by a lead wire 50. The fixed contact 48 of relay .2 is connected with lead wire 50 by the lead wire 52. The movable contactor 46 of relay 42 is connected with junction 54 by a lead wire 56. It is seen that the relay actuating coil 44 will be energized whenever the switch contactor 26 connects lead wire 18 and junction 23.

60. Theresistor 58 is connected with lead wire 62 wherecontact 72 that distributes current to fixed electrodes or contacts 74 in the'distributor cap 76. The electrodes 74 feed the spark plug 77 of the engine 16 by means of lead wires 78. Only one lead wire 78 and one spark plug 77 is illustrated in the drawing but it will be apparent to 'those skilled in the art that there will be as many lead wires 78ers there are spark plugs '77 and that there will also be as many electrodes '74 as there are spark plugs.

The rotor contact 72 is driven by the engine 16.

The ign'itionsystem includes an NPN transistor hit.

'The collector electrode of transistor 84? is connected with the primary winding 66 of ignition transformer 63. The emitter electrode of transistor St! is grounded as shown. The base electro'de of transistor 86) is connected with lead wire 82 which is in turn connected with junction 84. A resistor 86 is connected between junction $4 and ground.

The junction 84- is connected with a breaker contact 88 which becomes engaged and disengaged with the other breaker contact 96. The breaker contact 90 is carried by a breaker arm 92 which'is moved by a breaker cam 94- driven in synchronism with the engine 116. As the breaker cam 94 rotates, the contacts 88 and 90 are opened and closed in a manner well known to those skilled in the art. The breaker contact 90 is connected with resistor 96 and the opposite side of this resistor is connected with'junction 98 via the lead wire ltitl.

When the operator of a motor vehicle desires to start the engine 16, the switch contactor 26 is shifted to a position wherein it contacts both fixed contacts 22 and 24. In this position of the switch contactor 26, the coil 30 will be energized to cause the closure of contacts 32 and 34. With contacts 32 and 34'closed, the starting motor 36 isenergized and cranking of the engine 16 will begin. As the engine 16 is being cranked, the breaker cam 94 causes the contacts 88 and 90 to open and close and also causes the rotor contact 72 to sweep by the fixed electrodes 74.

When contactor 26 engages the contact 24, a circuit is now completed for the, relay actuating coil 44. If the voltage appearing between junction 12 and ground is greater than 9 volts, the contacts 46 and48 will separate. Assuming however that this voltage has dropped below 9 volts, the relay contacts46 and 4-8 remain engaged. The' resistor 58 is therefore shorted out of the circuit by a circuit that maybe traced from lead wire 18, through closed contacts 26 and 24, through lead wire a through lead wire'52, through closed contacts 46 and 48 and then through lead-wire 56 to'junction 54. t

, The primary circuit of the ignition system ext'ends from junction 98 toground and includes resistor 58, junction 54, resistor as, primary winding 66 and the emitter-collector circuit of transistor 80. Since the system voltage nected by resistor 86. This substantially equalizes the potential of the emitter and base electrodes of transistor 80 and causes the transistor 80 to be driven to a substantially fully nonconductive state between its collector'and emitter electrodes. When this occurs, the primary current is interrupted and a large voltage is induced in the seeondary' winding 70 which is applied to the" spark plug '77 via rotor 72, a fixed electrode 74' and the lead wire 78. The openingand' closingof the contacts as and 8% cause the transistor'St) to switch onand-ofi and cause ignition pulses tobe appliedto the spark plugs of the engine 16. s

Once the engine 16 has been started, the operator shifts the contactor 26 so that itno longer engages fixed contact 24 but remains engaged with fixed contact 22.

r In this position of the switch 'contactor 26,the relay coil 44 can no longer be energized and there is no short circuiting of the resistor 58 sincethe circuit to'leadwire St} has now been opened. The engine then continues to operate with the breaker contacts'88 and "90 opening and closing to control the conductivity of the transistor 80.

If the system voltage between junction 12 and ground should remain'above 9 volts when cranking of the engine 16 occurs, the relay coil 44 will cause the contacts 46 and '48 to be separated. The resistor 58 will then be in the primary circuit of the ignition system during cranking of the engine. 'It thus is seen that whether or not the resistor 58 is in the primary circuit'depends on whether or not the system voltage'is above or below 9 volts and also depends on whether or not the contactor 26 is iuengagement with fixed contact 24. Under running conditions where the contactor 26 engages the fixed contactZZ, the resistor 58 will always be in the primary circuitof'the ignition system. I 7

"In the particular embodiment of FIGURE 1, the transistor stlfis'shown controlled by breaker contacts 88 and 90. It is'a'pparent to those skilled in the art that "other means operated in synchronism with engine '16 might be used "to'control the conductivity of transistor "twsuch asadeVice'that generates pulses of voltage in gineicomprising, a source of direct current voltage, an

' ignition coilhaving a primary winding and a secondary has dropped below 9 volts, the resistor 58 is short cir- I cuited so the primary circuit is actually from junction 54, through resistor 60, through primary winding 66 and through the emitter-collector circuit of transistor 80.

through closedcontacts 90 and' 38, through lead Wire $2 and then through the, base to emitter junction of transistor 8%). With transistor 80 nowconductive between itscollector and emitter electrodes, current flows through the primary winding 66 and flux is built up in the ignition transformer 68. 7,

When breaker contacts 38 and 9t? separate, there no longer is a base current path for transistor {it} and the emitter and base electrodes of transistor w are conwinding, a resistor, a transistor "having emitter, collector and base electrodes, a primary circuit for' said ignition system energized from said voltage-source including. said resistor, said primary winding and the emitter-collector circuit of said transistor,'means for causing the conduc tivity of said transistor to vary ineits emitter-collector circuit in timed relationship with operation of said engine,

arelay having an actuating coil and a pair of normally 'closed contacts, said contacts remaining closed when a" voltage is impressed across said actuating coil which is below a predetermined value and opening when :said

voltage is above said predetermined value, a circuit for bypassing said resistor including the switch contacts of said relay, and means connecting said relay actuating coil across saidsourc'ecof direct current voltage. f

2. In combination, a source of direct current voltage,

an ignition coil having a primary winding and a secondary winding, a transistor havingemitter, collector and base electrodes, a resistor, a primary circuit energized from said'source of voltage including said resistor, said primary'winding and the emitter-collector circuit of said transistor, means operating in'timed relationship with 7 said. engine for controlling the conductivity of said transistor in its emitter-collector circuit, an electric cranking 7 motor, a switch for controlling the energization of said cranking motor fromsaid voltage source, an accurately calibrated relay includingan actuating coil and'a pair impressed across said actuating coil that is greater than a predetermined value, said contacts remaining continuously closed when the voltage impressed across said actuating coil of said relay is less than said predetermined value, a circuit bypassing said resistor including sa1d relay switch contacts, and .means connecting one side of said relay contacts and one side of said actuating coil with one side of said switch.

I 3. In combination, a source of direct current voltage,

, switch means operabletoconnect one side of said source of direct current voltage with first and second conductor means and operable toconnect said one side of said voltage source with only one of said first or second'conductor means, an ignition coil having a primary winding and a secondary winding, a resistor, a transistor having emitter, collector and base electrodes a primary circuit including said resistor, said primary winding and the emittercollector circuit of said transistor, means connecting one side of said primary circuit With said first conductor means, an electric cranking motor, said electric cranking motor being energized when said switch means connects one side of said source of voltage with said second conductor means, a relay having an actuating coil and a pair of normally closed contacts, said relay maintaining said contacts closed when the voltage impressed across the relay actuating coil is less than a predetermined value and opening said contacts only when a voltage is impressed across the relay actuating coil which is greater than said predetermined value, a bypassing circuit connected across said resistor including said relay switch contacts, and conductor means connecting one side of said relay actuating coil with said second conductor means.

4. An ignition system for an internal combustion engine comprising, a source of direct currentvoltage, an ignition coil having a primary winding and a secondary winding, a transistor having emitter, collector and base electrodes, a primary circuit for said ignition system energized across said source of direct current voltage including said primary winding and the emitter-collector circuit of said transistor, means operating in timed relationship with said engine for controlling the conductivity of said transistor in its emitter-collector circuit, and a voltage responsive control means responsive to at least two different voltage magnitudes having sensing terminals connected with said source of direct current, said voltage responsive control means including means connected in said primary circuit for varying the resistance of said primary circuit, said voltage responsive control means being operative to provide a primary circuit resistance which has a predetermined value when said voltage responsive control means senses a source voltage which is below a predetermined value and increasing said primary circuit resistance when said voltage responsive control means is sensing a source voltage which is above said predetermined value.

5. An ignition system for an internal combustion engine comprising, a source of direct current voltage, a transistor having emitter, base and collector electrodes, an ignition coil having a primary winding and a secondary winding, a resistor, a primary circuit for said ignition system including in a series connection, said resistor, said primary winding and the emitter and collector electrodes of said transistor, means for varying the conductivity of said transistor in timed relationship with said engine, and voltage responsive control means having voltage sensing terminals coimected with said source of direct current voltage and operative to short circuit said resistor from said primary circuit when the voltage that said voltage responsive means is sensing drops below a predetermined value, said resistor remaining continuously in said primary circuit when the voltage that said Voltage responsive control means is sensing is above said predetermined value.

6. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a three terminal semiconductor having a pair of current carrying terminals and a control terminal, a primary circuit for said ignition system including in a series connection, the control terminals of said semiconductor and said primary winding energized across said source of direct current voltage, means connected with the control terminal of said semiconductor for controlling its conductivity in timed relationship with said engine, a voltage responsive control means having voltage sensing terminals connected across said source of voltage and including means connected in said primary circuit to vary the resistance of said primary circuit, said voltage responsive control means being operative to provide a primary circuit resistance which has a predetermined value when said voltage responsive means is sensing a voltage which has a predetermined value and being operative to increase said primary circuit resistance when said voltage responsive means is sensing a voltage which is above said I predetermined value said primary circuit resistance remaining at its increased value as long as the voltage responsive means is sensing a voltage which is above said predetermined value.

7. The ignition system according to claim 6 wherein the three terminal semiconductor is a transistor.

8. An ignition system for an internal combustion engine comprising, a battery, an ignition coil having a primary winding and a secondary winding, a three terminal semiconductor having a pair of current carrying terminals and a control terminal, a primary circuit for said ignition system including the control terminals of said semiconductor and said primary winding, means connected with the control terminal of said semiconductor for controlling the conductivity of said semiconductor in timed relationship with said engine, a voltage responsive control means connected in said primary circuit which includes means that is operative to vary the resistance of said primary circuit, said voltage responsive control means having a pair of voltage sensing terminals, an electric cranking motor for cranking said engine, a switch means operative to simultaneously connect said primary circuit across said battery and to connect the voltage sensing terminals of said voltage responsive means across said battery, said voltage responsive control means being operative to provide a primary circuit resistance which has a predetermined value when said voltage responsive means is sensing a battery voltage which is a predetermined value and being operative to increase said primary circuit resistance when said voltage responsive means is sensing a battery voltage which is above said predetermined value.

9. An ignition system for an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a semiconductor, a resistor, a primary circuit for said ignition system including in a series connection said semiconductor, said primary winding and said resistor, a source of direct current voltage, a voltage responsive means having switching terminals and voltage sensing terminals, said switching terminals being connected across said resistor whereby said resistor is shorted when said switching terminals are connected, an electric starting motor for cranking said engine, a

switching means for simultaneouslyenergizing said electric cranking motor and for connecting said primary circuit across said source of voltage, said switching means connecting the voltage sensing terminals of said voltage responsive means across said source of direct current voltage when said starting motor is energized, said voltage responsive means opening the circuit between its switching terminals when said source of direct current voltage is above a predetermined value and maintaining a ing anda'secondary winding, a semiconductor, a resistor,

a primary circuit for said ignition system including in a series connection said semiconductor, said primar winding and said resistor, a battery, a relay having an ac-. tuating coil and normally closed switch contacts, said contacts of saidrelay being connected across said resistor whereby said resistor is bypassed when-said contacts are, closed, an electric starting motor for cranking said engine, means for energizing said relay actuating c0i1, said primary circuit and said electric cranking motor from said battery when said engine is being cranked including manually operable, switch means, said relay being calibrated such that said relay contacts remain continuously predetermined value.

a a closed when thetterminal voltage of the, battery is'below a predetermined value and open said relay contacts when the terminal voltage of the battery is higher than said References Cited by theExaminer UNITED STATES PATENTS 1 1,915,982 6/33 Doman 290'35 1,957,127 5/3'4' Arthur 290- 37 2,723,654 11/55 Hartzell 123-'-179 2,867,729 9/57 Redick' 1239-179 2,846,992 8/58 Short 123-148 X 2,966,615 12/60 Meyer l23-l48 X 3,019,782, 2/62 Kuritza 123148 X 3,020,964 2/62 Kerr 315209 3,046,447 7/62 Kirk 3l5-'209 oars L. RADER, Primary Examiner. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, A SOURCE OF DIRECT CURRENT VOLTAGE, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A RESISTOR, A TRANSISTOR HAVING EMITTER, COLLECTOR AND BASE ELECTRODES, A PRIMARY CIRCUIT FOR SAID IGNITION SYSTEM ENERGIZED FROM SAID VOLTAGE SOURCE INCLUDING SAID RESISTOR, SAID PRIMARY WINDING AND THE EMITTER-COLLECTOR CIRCUIT OF SAID TRANSISTOR, MEANS FOR CAUSING THE CONDUCTIVITY OF SAID TRANSISTOR TO VARY ITS EMITTER-COLLECTOR CIRCUIT IN TIMED RELATIONSHIP WITH OPERATION OF SAID ENGINE, 